Marshall,
Integration with SAP ERP has two main areas:
1. master data
2. transactional data such as sales orders
Sounds like you have co-deployment scenario where SAP ERP and yMKT are running on the same HANA system. In that case, you could do scema mapping to point yMKT's ERP schema and run extract reports CUAN_IC_MASTERDATA_EXTR_FULL/DELTA. This will get the contact master data loaded into interaction contacts.
Then if you use "Customer" based segmentation profile, you can even segment sales data automatically as HANA views point to ERP schema. if you need to use "contact" segmentation profile, then you have develop custom HANA views on top of ERP sales data tables to bring it into segmentation.
Hope this helps
Thanks
-Bharath